Following our notification, Symantec published a report in response to our inquiries and disclosed that 23 test certificates had been issued without the domain owner’s knowledge covering five organizations, including Google and Opera.

However, we were still able to find several more questionable certificates using only the Certificate Transparency logs and a few minutes of work. We shared these results with other root store operators on October 6th, to allow them to independently assess and verify our research.

Symantec performed another audit and, on October 12th, announced that they had found an additional 164 certificates over 76 domains and 2,458 certificates issued for domains that were never registered.

It’s obviously concerning that a CA would have such a long-running issue and that they would be unable to assess its scope after being alerted to it and conducting an audit. Therefore we are firstly going to require that as of June 1st, 2016, all certificates issued by Symantec itself will be required to support Certificate Transparency. In this case, logging of non-EV certificates would have provided significantly greater insight into the problem and may have allowed the problem to be detected sooner.

After this date, certificates newly issued by Symantec that do not conform to the Chromium Certificate Transparency policy may result in interstitials or other problems when used in Google products.

The technology is designed for cross-browser compatibility: to a large extent the API is compatible with the extension API supported by Google Chrome and Opera. Extensions written for these browsers will in most cases run in Firefox with just a few changes. The API is also fully compatible with multiprocess Firefox.